All maintenance parts and equipment must either be carried up on somebody's back or pulled up in a dumb-waiter.

People in some urban areas shoot the heck out of cables.

They think the cables transmit camera images from intersections

They shoot up the cables before committing crimes

Some of the cables do transmit camera information....smart traffic management, for instance.

Cables are designed with redundancy but 90% of the redundancy is already used up

It is highly improbably that any of the people shooting these cables are members of the NRA

Nearly all of the auxilliary systems that were submerged at Fukushima were on the ground floor.

In the US, all of those systems in Nuclear facilities are on the second floor and are partitioned off into separate, environmentally sealed rooms.

The newest generation of US Nukes are a throwback to the Nimitz design.

Nimitz demanded noise free, pump free designs.

The downside of the Nimitz reactor is power density. They are big for the power produced.

Size is less of a restriction in a stationary power plant than in a submarine or surface ship.

New reactor cores will be at the bottom of very, very deep water vessels.

"Over-heat" will reduce the density of the water (think steam pockets if that helps). Lower density water means that neutrons will not be slowed down enough to be captured by U nuclei. The reaction becomes self-quenching.